Freescale MC33978/34978 Switch Detection Interface ICs are a multiple switch detection interface (MSDI) device which is designed to detect the closing and opening of up to 22 switch contacts in automotive or industrial environments. The switch status, either open or closed, is transferred to the microprocessor unit (MCU) through a serial peripheral interface (SPI). This SMARTMOS device also features a 24-to-1 analog multiplexer for reading analog inputs. The analog input signal is buffered and provided on the analog multiplexer (AMUX) output pin for the MCU to read. Individually selectable input currents are available in Normal and Low-Power Mode (LPM), as needed in the application. A battery and temperature monitor are included in the IC and are available via the AMUX pin. This product interfaces with any microcontroller that supports SPI communications.